There's a way you can resolve that. At least in theory. - Make a copy of your campaign, then roll back the original. "Settings - Roll Back Game". Use the transmogrifier to bring in NPCs and maps you created the same day that the player made the change. Manually adjust things like status, hit points, etc. that happened since the morning snapshot you rolled back to. Now, this requires Pro. The roll20 wiki seems to suggest you can do this even if you're not Pro at the time the mistake is made: Roll Back Game
The Game's Creator must be a Pro subscriber to
have access to this feature. Between the hours of 4 and 6 AM PST, a save
state is made for every game on Roll20. Seven days’ worth of save
states are kept on file before they’re rewritten with new save states.
Pro users have the ability to roll back their game to any save state
available from the past seven days to correct any drastic mistakes made
to their game.
Note the "a save state is made for every game on Roll20". Presumably every game, regardless of subscriber status. You can run with that and subscribe to Pro and just test it; or you can wait until someone more knowledgeable confirms that this is indeed how it works and you don't have to be Pro for the save state to be created, you just have to be Pro to be able to get back to it. Note the 7-day time limit, don't let that expire. Pro is most definitely worth it if you love immersion and "easy button". Things like being able to roll saving throws for groups of monsters (GroupCheck), bring groups of monsters into Initiative (GroupInit), show health of monsters as an aura, bump monsters to the GM layer and back, calendar, blood spatter as things start to die, graphical turn tracker, easy transformation for druids, the list goes on. API scripts are amazing. I'm always happy to show people how I've got scripts set up in my own games, and what that does for running the game.

Dom said: Is there a way I can copy the PC from the rolled back game to the recently saved game? Yes; you can use the Character Vault to save import the old Character from the Game's old savestate. Then, roll the Game forward and use the Character Vault to export the old Character to the recent savestate. The Transmogrifier can also be used to this effect.